The long-term goal of the project is to contribute to the body of scientific information concerning the comparative anatomy and evolution of the vertebrate inner ear. Current investigations center about the basilar papilla in urodele amphibians, the papilla neglecta and basilar papilla in reptiles, and the papilla neglecta in the laboratory mouse. SEM and TEM surveys are being made of the basilar papilla in representatives of the major evolutionary lines of caudate amphibians that retain the receptor to determine the nature of morphological and cytological differences that have appeared in the group. Studies of the reptilian basilar papilla and papilla neglecta are particularly concerned with the patterns of innervation and synaptic structures within the receptors. The development and adult structure of the papilla neglecta in the mouse is being investigated by light microscopy, SEM and TEM. BIBLIOGRAPHIC REFERENCES: Baird, I.L.: Some aspects of the structure of the papilla neglecta in the turtle, Pseudemys scripta. Anat. Rec., 187:529 (1977). White, J.S.: Fine structural features of the basilar and amphibian papillae in the tiger salamander, Ambystoma tigrinum. Anat. Rec., 187:747-8 (1977).